Array antennas are used for a variety of different applications. Array antennas may be constructed using a plurality of three-dimensional (3D) antennas. These arrays are typically configured as a rectangular lattice but other geometries are also possible. Additionally, these antennas may be used separately, and not as part of an array. In certain embodiments, the 3D antennas may comprise notch antenna elements. The term “notch antenna” is intended to include tapered and flared elements, such that the shape is not limited by this disclosure.
Each notch antenna element includes an electrically conductive body, referred to as a notch radiator element, which has a slot. The slot separates the notch radiator element into two prongs. One of the prongs may be grounded while the other prong is energized by an RF signal. In general, the energized prong conveys energy from a feed port into free space or air, or visa-versa. The feed port may have a characteristic impedance relative to the system impedance for maximum power transfer. The propagating signal leaving the feed port is in communication with the tuned gap between the energized prong and the other prong. This gap is optimized with other dimensions to result in wideband operation. The propagating signal conveys energy into the notch slot and then into free space or air. The antenna feed port may convey energy to and from the antenna system at its characteristic impedance. Between this feed port and the radiating element are a variety of possible architectures creating a characteristic impedance match over the desired operational frequency band. For example, in certain embodiments, a PC board may be used to carry the propagating signal. In other embodiments, a PC board may not be used.
These notch antennas may be combined to form ultra-wideband array systems. Ultra-wideband low loss phased array systems are desired in the cellular, telemetry and military applications. Use of this technology in these areas allow greater flexibility in achieving compact, lower cost, higher performance designs.
FIG. 1 shows one such notch antenna that may be used as part of an ultra-wideband array system. In this figure, a portion of an ultra-wideband array system is shown. The ultra-wideband array system extends in two dimensions, and FIG. 1 represents a periodic unit cell 1 of that ultra-wideband array system. The unit cell includes two notch antennas, one disposed on each of the front sides of the unit cell. The back facing sides contain the remaining portion of the front element sides of adjacent unit cells, making up 2 dual polarized elements in an infinite array configuration for electromagnetic (EM) modeling.
As described above, each notch antenna 10 includes an energized prong 11 and a grounded prong 12. The energized prong 11 and the ground prong 12 are separated by a slot 14. Each of these prongs is shared by two notch antennas, disposed on two orthogonal sides of the unit cell 1. An electrical feed, such as a coaxial transmission line 13, passes through the lower portion of the grounded prong 12, and enters the energized prong 11. This coaxial transmission line 13 may be carrying a RF signal to the energized prong 11. To insure proper operation, a coaxial transmission line 13 is used to convey energy between the radiating element and an input feed port. A dielectric insert may or may not be used in the coaxial transmission line 13. The antenna bandwidth (BW) and performance is a function of the total geometry including the size and shape of the slot 14. In this embodiment, the slot 14 comprises three different gap widths, with the smallest gap being at the bottom and the largest gap being at the top. The geometry of the slot 14 and the characteristics of the RF signal are some of the variables that may be tuned in creating the optimal ultra-wideband array system.
Therefore, it would be beneficial if there were a notch antenna that could have a greater range of impedance tuning, resulting in a wider bandwidth for a given height. Further, it would be advantageous if this system was also cost effective, robust, relatively easy to manufacture, and retained a lower profile.